A conventional rotary electric machine control apparatus controls driving of a rotary electric machine by controlling on/off operations of switching elements of a power conversion device. According to an exemplary rotary electric machine control apparatus disclosed in JP-A-2004-248466 (patent document), a CPU generates command signals for commanding on/off operations of switching elements and a driver IC generates gate signals for the switching elements in correspondence to the command signals. When the gate signals generated by the driver IC are outputted to the gates of the switching elements, the switching elements are turned on and off in response to the gate signals thus rotationally driving the rotary electric machine.
According to the exemplary rotary electric machine control apparatus, a pair of switching elements, that is, a high-side switching element and a low-side switching element, is provided for each phase of multiple-phase coils of the rotary electric machine. The CPU therefore needs to generate command signals for the pair of high-side and low side switching elements, respectively. The CPU generates two command signals for each phase and applies the generated two command signals to a driver IC through the CPU output terminals, signal wires and driver IC input terminals, respectively. As a result, the number of the output terminals, the signal wires and the input terminals between the CPU and the driver IC is doubled relative to the number of phases of the coils. For example, in a case of three phase coils, the numbers of the CPU output terminals, the signal wires and the driver IC input terminals are six, respectively.
In a case of application of the exemplary rotary electric machine control apparatus to an electric power steering system, the rotary electric machine control apparatus need be compact-sized for installation in a limited space. For reducing a size of the rotary electric machine control apparatus, sizes of a CPU and a driver IC need be reduced and areas of a substrate for mounting the CPU and the driver IC thereon need be reduced. In a case of the exemplary rotary electric machine control apparatus, a number of CPU output terminals, signal wires and driver IC input terminals need be provided between the CPU and the driver IC. As a result, reduction of sizes of the CPU and reduction of areas of the substrate for mounting the CPU and the driver IC are limited. It is thus not possible to sufficiently reduce the size of the rotary electric machine control apparatus.